Alkylated methylenedianiline tars

ABSTRACT

Alkylated methylenedianiline tars having the formula   WHEREIN EACH R is independently a secondary 2-alkyl radical having from about three to about 10 carbon atoms and n is from about 0.7 to about 1.2.

United States Patent 1191 Gardiner Dec. 18, 1973 '[22] Filed:

[ ALKYLATED METHYLENEDIANILINE TARS 75 inventor: Robert Archie Gardiner,

- Wilmington, Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

Jan. 20, 1972 21 Appl. No.: 219,526

3,004,916 10/1961 Ertelt ..252/32.7

Primary ExaminerWerten F. W. Bellamy ArtorneyFrancis J. Crowley 5 7ABSTRACT .Alkylated methx ens enilir eFee, aY the formula wherein each Ris independently a secondary 2-alkyl radical having from about three toabout 10 carbon atoms and n is from about 0.7 to about 1.2.

5 Claims, N0 Drawings 1 ALKYLATED METHYLENEDIANILINE TARS BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates tocompositions consisting essentially of alkylated aromatic polyamines andmore particularly to alkylated methylenedianiline tars which are usefullubricant additives.

2. Description of the Prior Art To meet the requirements of moderntechnology, lubricants are usually compounded with additives. Alubricant additive may be defined as a material which imparts a new anddesired property not found in the original base lubricant or whichproperty reinforces one or more desirable properties already possessedto some degree by the base lubricant. Additives designated asantioxidants, corrosion inhibitors, rust inhibitors, ex-

treme pressure agents, anti-stain agents, anti-wear agents, viscosityindex improvers, pour point depressants, detergents, dispfersants andthe like are well recognized in the art. Lubricant bases into which suchadditives are blended include not only those derived from petroleumsourcesbut synthetic lubricants as well. Synthetic lubricant bases ofsuch types as aliphatic esters, polyalkylene oxides, silicones andfluorine-containing materials, for example, are also improved by theaddition thereto of selected lubricant additives.

Most often the environment in which a lubricant is used is such that thelubricant comes into contact with air and metals which may. function aspro-oxidants, often at elevated temperatures. Under such conditions, thelubricant, whether it be mineral oil based or synthetic based, undergoesa series of oxidation reactions whereby the viscosity of the lubricantis increased and carbonaceous deposits and acidic by-products areformed. The increase in viscosity and the formation of carbonaceousdeposits may lead to impairment of lubricating ability of the lubricant,and the formation of acidic by-products may lead to increased corrosionof the metal parts which are in contact with the lubricant. Antioxidantsare, therefore, regarded among the more important additives used inlubricant compositions. Lubricants protected by antioxidants includelubricating oils, synthetic lubricants and grease compositions. Classesof organic compounds used in the art as antioxidants include sulfides,disulfides, sulfoxides, phosphites, amines, phenols, selenides and zincdithiophosphates. Particular choice of an antioxidant of course dependsupon the lubricant base employed and the intended use of the lubricant.

Amines, particularly aromatic amines, have been used extensively asantioxidants in lubricants because of their effectiveness and becausethey possess desirable auxiliary properties such as good solubility inlubricant bases, compatibility with other additives, and their readyavailability. In general the aromatic amines useful as antioxidants arethose "wherein the amine nitrogens contain alkylor aryl substituents asexemplified by N-phenyl-alphanaphthylamine, N-phenyl-betanaphthylamine,tetramethyl-diamino-diphenylmethane and phenothiazine.

It is also, however, recognized in the art that in addition to beingeffective for the intended antioxidant purpose and satisfactory in otheradditive requirements, such as solubility, a lubricant additive mustalso be economical to produce in order to obtain commercial acceptance.

Cyba et al. in U.S. Pat. No. 3,011,976 disclose lubricant compositionscontaining 4,4-di-(sec. alkyl)-4,4'- diamino-diphenylmethane andN,N,N',N-tetra-(sec. alkyl)4,4'-dimainodiphenylmethane wherein the abovediphenylmethane derivatives are obtained by reductivealkylation of4,4-diaminodiphenylmethane.

SUMMARY OF THE INVENTION This invention is directed to compositionsconsisting essentially of alkylated aromatic polyamines having theformula wherein each R is independently a secondary 2-alkyl radicalhaving from about three to about 10 carbon atoms and n is from about0.07 to about 1.2. Also included within this invention are lubricantscomprising a lubricant base and a stabilizing amount of one or more ofthese compositions.

DESCRIPTION OF THE INVENTION This invention relates to compositionsuseful as lubricant additives. These compositions consist essentially ofalkylated aromatic polyamines of the formula wherein R is a secondary2-alky1 radical having from about three to about 10 carbon atoms andwherein n is from about 0.7 to about 1.2.

As is well known in the art, methylenedianilines are muchdesiredcommercial compositions because of the versatility of their uses,e. g., in the preparation of epoxy resins, polyamides, polyimides,polyureas and polyurethanes and specifically 4,4-methylenedianiline isalso used extensively as an intermediate in the preparation4,-4'-methylene-dipheny1diisocyanate which is used in preparation ofpolyurethane polymers and as an intermediate in the preparation ofantioxidants. These methylenedianilines are usually prepared by reactinganiline with formaldehyde in the presence of a strong acid catalyst suchas hydrochloric acid, sulfuric acid, perchloric acid, hydrobromic acid,boron trifluoride, tin

tetrachloride, phosphorus chloride, phosphorus oxychloride, thionylchloride, aluminum chloride and the like. In this reaction variousisomeric methylenedianilines may be produced, including the 4,4-isomer,the 2,4'-isomer and the 2,2-isomer. In the usual condensa tion the4,4'-isomer is present to the extent of about 90 percent and the2,4'-isomer is present to about percent, there being very small amountsof 2,2'-isomer present. For certain applications of themethylenedianilines, such as their use in the preparation ofpolyisocyanates with lower tendency to crystallize, a higher proportionof 2,4'-isomer is desirable, and by careful control of the aniline toformaldehyde ratio and of the aniline to water ratio, isomeric mixturescontaining up to 35 percent of the 2,4'-isomer can be prepared (see'U.S. Pat. No. 3,277,173 The yield of methylenedianiline from thecondensation of aniline with formaldehyde normally ranges from about 40percent to about 85 percent depending upon the particular processconditions.

When higher conversions and higher yields of the methylenedianilines aresought by the usual procedures of changing reactant ratios or byextending the heating time, the amount of unusable by-product is alsoincreased. For example, when the 4,4'-isomer of methylenedianilinehaving the formula and the 2,4'-isomer having the formula react furtherwith another molecule of formaldehyde and another molecule of aniline,identical products having the formula are obtained.

Further condensation of the triamine (I) above, with formaldehyde andaniline, will produce a tetra-amine having the formula -C ILQNH: 7 QB: HI NH: NH: (II) It is also possible that the 2,2-isomer which is presentin very small amounts may also react further with formaldehyde andaniline to form a triamine which may be designated as2,2'-diamino-5-(methylene-paminophenyl)-diphenylmethane, however, theamount of such triamine which may be present is so small that for allpractical purposes, the triamine may be considered to be entirely thatexemplified by (l).

The above described triamine (l) and tetra-amine (ll) are formed notonly during the condensation reaction process itself but also duringdistillation recovery of the methylenedianilines, and particularly whensuch distillations are carried out to recover the last possible amountsof methylenedianilines by either prolonged heating or heating at highertemperatures. Thus, since from about 40 to about percent of the startingmaterials used in the distillation of methylene-dianiline go into themethylenedianiline itself, the remaining about 60 to about 15 percent ofthe starting materials can be said to go into the methylenedianiline tarresidue. There being little practical utility for the abovedescribedmethylene-dianiline tar residues, often referred to as tars, they areusually discarded and, since there are no ready means for theirdisposal, they are burned by costly and time-consuming means. It isclear, therefore, that if any useful products can be prepared from thesepresently discarded methylenedianiline tar residues, such tar residueswill afford a very inexpensive source for the starting materials used inthe preparation of such useful products.

It has now been discovered that by reductive alkylation ofmethylenedianiline tar residues with methyl ketones containing fromabout three to about 10 carbon atoms, compositions useful as lubricantadditives are obtained and moreover it has been discovered that suchalkylated methylenedianiline tars are more effective as lubricantantioxidants than the alkylated methylenedianilines themselves.

As discussed above, the methylenedianiline tar residues are primarilymixtures of aromatic polyamines, there being present some4,4'-methylenedianiline, 2,4'- methylene-dianiline,2,2-methylenedianiline, triamine exemplified by formula (I) and sometetra-amine exemplified by formula (II). The amount ofmethylenedianilines present in the tar will, of course, depend upon theefficiency of the methylenedianiline recovery process, but in most casesmethylenedianilines make up less than about 10 weight percent, andusually about three to about five weight percent of the tar residuesobtained. The major portion of the methylenedianiline tar residue is thetriamine of formula (I). The tetra-amine (ll) normally makes up lessthan about five weight percent of the tar residue, but this too can varyaccording to the condensation and recovery processes.

The composition of the methylenedianiline tar residue may be representedby the formula where the tar residue is a tetra-amine as in formula(ll), n in formula (III) is 2. However, since the tar residue isnormally a mixture, the composition can be best represented by someintermediate value of n. Thus in an illustrative example of a mixture,where the tar is composed of percent by weight of methylenedianiline and90 percent by weight of triamine of formula (I), n will have a value of0.87. It should be noted that the weight percentages of triamine,tetra-amine and methylenedianiline set out above are typically found inthe tar residue, but as stated, the percentages of each may be greateror less depending on the various considerations mentioned previously.

The table below shows the values for n for various typical and atypicalcombinations of aromatic amines in the tar. In the table, MDA refers tomethylenedianiline, triamine refers to a compound as exemplified byformula (I) and tetra-amine refers to a compound as exemplified byformula (II). The given value for n is weighted average of the n valuesof the components of the mixture.

Table MIXTURES OF AROMATIC POLYAMINES Mixture Weight Mol. n l. MDA 2028.7

triamine 80 7L3 0.7] 2. MDA 21.3

triamine 85 78.7 .79 3. MDA 10 13.4

triamine 90 86.6 0.87 4. MDA 5 7.7

triamine 95 92.3 0.92 5. MDA l 1.4

triamine 99 98.6 0.99 6. MDA l0 7.6

triamine 80 78.2 0.93

tetra-amine 10 I42 7. triamine 90 92.4 l.08

tetra-amine [O 7.6 8. triamine 75 80 L2 tetra-amine It has been found byanalytical means, including gas chromatography and nuclear magneticresonance spectroscopy, that a typical methylenedianiline tar residuecontains less than 10 percent by' weight of methylenedianiline, lessthan about 5 percent by weight of tetraamine and that the majority'ofthe tar is made up of triamine of formula (I). Thus in formula (III) forthe methylenedianiline tar residue, a typical tar will have a value of nin the range of from about 0.85 to about- 0.99. Tar residues having an nvalue of from about 0.7 to about 1.2 are however still economical to usesince they do not contain as. much expensive MDA as to appreciablyincrease their cost and they do not contain sufficient MDA andtetra-amine to reduce their overall effectiveness as starting materialsfor the production of the effective lubricant additives of thisinvention. These tars are therefore useful inthe preparation of theadditives of this invention.

The compositions of this invention are prepared by reductive alkylationof a methylenedianiline tar residue. This reductive alkylation iscarried out by treating the tar residue in excess methyl ketonespreferably having from about three to about 10 carbon atoms (e.g.,solvent quantities) with hydrogen at 100C. to 250C. in the presence of asuitable catalyst system. Suitable catalysts include the usualhydrogenation catalysts such as platinum, palladium, cobalt or nickel,either as such or carried on a suitable support, such as carbon. Thereaction system may also contain catalysts which are known to promotecondensation of carbonyl compounds with aromatic amines to form anils;such catalysts include zinc chloride, acetic acid, phosphoric acid,alkyl acid phosphates and the like. Under the usual reaction conditionsthe products obtained are mono-substituted amine derivatives, i.e., eachof the amino nitrogen has only one secondary alkyl group attachedthereon. Thus the product obtained upon reductive alkylation of themethylenedianiline tar residue may be represented by l in wherein n isfrom about 0.7 to about 1.2

Since the ketones useful in forming the compositions of the inventionare methyl ketones of three to 10 carbon atoms the alkyl group attachedto the amino nitrogen of the resultant aromatic polyamines are secondary2-alkyl groups which may be represented by the formula -Cl-l(CH )---Rwherein R is an alkyl group having from one to about eight carbon atoms.The useful ketones are therefore methyl alkyl ketones wherein the alkylportions are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl andoctyl as well as the various isomeric forms of the latter six alkylgroups. Specific, but non-limiting examples thereof include acetone, 2-butanone, Z-pentanone, 4-methylbutane-2-one, 2- hexanone,4-methylhexane-2-one, 2-heptanone, 5- methylhexane-Z-one,5,6-dimethylhexane-2-one, 5,S-dimethylhexane-Z-one,4,5-dimethylhexane-2-one, 4-ethyl-heXane-2-one, 5-ethylhexane-2-one, 2-nonanone, 6-methyloctane-2-one, 5,5-dimethylheptane-2-one,4,5-dimethylheptane-2-one, 4,5,5-trimethylhexane-Z-one,5-ethylheptane-2-one, 4- ethylheptane-Z-one, 2-decanone,7,7-dimethyloctane- 2-one, 6-ethyloctane-2-one, and the like. Thepreferred ketone is S-methylhexane-Z-one so the preferred R group in thealkylated methylene dianiline tar of formula (III) is As statedpreviously, the ketones used in the reductive alkylation are methylketones having preferably' from about three to about 10 carbon atoms.When methyl ketones containing from about three to about six carbonatoms are used, the resultant alkylated methylenedianiline tar residuesare not very soluble in 7 liquid lubricant bases, however, theseproducts are effective antioxidants in lubricant compositions such asgreases wherein complete solubility in the lubricant base is notnecessarily required. When high solubility in lubricant bases isdesired, methyl ketones of from about six to about 10 carbon'atoms areused in the reductive alkylation process. While methyl ketonescontaining more than 10 carbon atoms are useful in the preparation ofthe alkylated products of the invention, thesluggishness of thereductive alkylation process and the limited availability of suchketones make them less desirable than the methyl ketones of three to 10carbon atoms. A mixture of methyl ketones may be used in the reductivealkylation process such that the resultant alkylated methylenedianilinetar will have a mixture of secondary 2-alkyl groups; however forsimplified operation it is more convenient to use a single methylketone.

In the reductive alkylation process the completion of the reaction isusually indicated by the cessation of hydrogen absorption. The alkylatedproducts may also be analyzed for the completion of alkylation byconventional procedures such as by infrared spectroscopy. If thealkylated methylenedianiline tar is to be used as antioxidant in greasecompositions, it has been found that complete alkylation is notnecessary whereas if the product is to be used in lubricating oils,complete alkylation is desirable to obtain the required solubility.

The alkylated methylenedianiline tar residues of this invention areeffective antioxidants in grease compositions and in lubricating oils.Unexpectedly, the alkylated methylenedianiline tar residues of thisinvention, as represented by formula (IV), n 0.7 1.2, are more effectiveas antioxidants in greases and in lubricating oil than alkylatedmethylenedianilines which contain the same secondary 2-alkyl groups(formula lV, n This fact is clearly borne out by the examples whichfollow. The present invention, therefore, provides effective antioxidantcompositions which are also very economical to produce since thestarting materials for their production are methylene-dianiline tarresidues which are ordinarily discarded at considerable expense.

The compositions of the invention can be blended with the lubricantbases in any of the conventional methods such as adding them to thelubricant base and mixing or adding the compositions as a solution in asuitable solvent followed by mixing and topping of the volatile solvent.In blending of the compositions of the invention into greasecompositions, the invention compositions may be added to the lubricantbases or added along with the grease thickeners. It will be readilyapparent to those skilled in the art that the alkylatedmethylenedianiline tar residues of the invention may be used inlubricant compositions together with other lubricant additives which arenormally used.

The following examples are intended to be merely illustrative of theinvention and not in limitation thereof. Unless otherwise indicated, allquantities are by weight.

EXAMPLE 1 This example illustrates the preparation of alkylatedmethylenedianiline tar residues. Tar residue obtained from themethylenedianiline manufacturing process was analyzed by vapor phasechromatography and found to contain about percent by weight methyl-Nuclear magnetic resonance (NMR) analysis indicated that the majorconstituent of the tar was the triamine represented by the formula Le.n=0.87 in the tormula HaNQCl-h-QNH:

10 Three hundred sixty Grams of the tar residue in 592 g.

of methylisoamylketone was charged into a 2-liter autoclave. To thismixture in the autoclave was added 4 g. of percent (A. R. Grade)phosphoric acid, 8 g. of tridecyl acid phosphate, 30 g. of ahydrogenation catalyst, i.e., 1 percent platinum metal on carbon (Darco6-60), and 20 g. of distilled water. The autoclave was pressurized withhydrogen (400500 psig) and then heated with shaking to about 170C.Hydrogenation was continued at 170C. and 400-500 psig hydrogen pressure.A major portion of hydrogen absorption occurred during the first 5 to 7hours and thereafter continued slowly foran additional 8 to 9 hours,after which the hydrogen absorption ceased. The total hydrogen pressuredrop was around 1,200 psig. The autoclave charge was filtered hot andthen topped at 150C. and 10 mm. pressure for 3-5 hours. The productobtained (628 g.) was a viscous transparent red material which washighly soluble (75 percent solution being readily obtained) in solventrefined neutral oil SUS/ 100F.). NMR analysis of the product indicatedthat the product obtained was mono-substituted amine derivative whereineach amine-nitrogen had only one methylisoamylmethyl group attachedthereon. This product is therefore represented by the formula wherein Ris methylisoamylmethyl and n is 0.87.

Using the same general operating procedure describe above, additionalalkylated methylenedianiline tar residues in this invention wereobtained using acetone, methylethylketone, methylisobutyl ketone,methylpentyl ketone and methylhexyl ketone. However, when ethylamylketone (octane-3-one) was used, no absorption of hydrogen took place.

EXAMPLE 2 This example illustrates the antioxidant activities and thesuperiority of the alkylated methylene-dianiline tar residues of thisinvention over the corresponding alkylated methylenedianiline when usedas additives in lubricating grease. The comparative test method was theOxygen Bomb Test, i.e., ASTM D-942, wherein a sample of greasecontaining the antioxidant additive composition is heated in a bomb to210F. (99C.) and the bomb is filled with oxygen at psi (7.7 kg. per sq.cm.), the pressure is then observed and recorded at stated intervals.The degree of protection afforded by the anti-oxidant composition iscompared in terms of number of hours required for the oxygen pressure todrop 25 psi. The grease utilized throughout the comin a single containerof the oil at 250F. for 168 hours while agitating with oil with air, andthen checking for the changes in the metals and the oil. The results aresummarized in Table III below. The alkylated compounds are designated asin Example 2.

TABLE IIL-CORROSION AND OXIDATION OF LIGHT OILS Test Conditions; 250 F.for 168 Hours Viscosity (cs. at 109 F.)

Cone P Acid number Metal coupons \vt. loss (g.) ereont Antioxidantpercent Before After change Before After Change Cu Mg Al Steel Cd 1Turbine oil (Sun Oil Co.) 32. 6 68. 7 110. 7 0. 02 12. 30 12. 2S 0. 0040 0 0 0. 21 2 Crsec. alkyl MDA 0. 05 32. 6 66. 4 103. 6 0. 02 13. 13. 0S0. 004 0 0 0 0. 09 3 C -sec. alkyl MDA-TAIL... 0. 05 32. 7 37. J 15. 90. 02 2. 60 2. 58 0. 003 0 0 0 0 4 .-d0 0. 50 32. 9 33. 3 1. 2 0. 02 0.05 0. 03 0 0 0 0 0 methylenedianiline isomers.

' TABLE! Grease Bomb Oxidation Test (ASTM D-942) Hours to 25 psiAntioxidant Cone, Wt.% Pressure Drop l. Control grease 0 47 2. C -scc.alkyl MDA 0.5 535 3. C -sec. alkyl MDA-TAR 0.5 854 4. C -sec. alkyl MDA0.5 682 5. C -sec. alkyl MDA-TAR 0.375 483 Since the methylenedianilinetar residue (MDA- TAR) used to prepare the above alkylated products maycontain up to 10 percent by weight of methylenedianiline and thus thealkylated tar residue may contain up to 10 percent of alkylatedmethylenedianiline, the following grease bomb oxidation tests werecarried out as above using the same antioxidants but at 0.04 weightpercent level. The results are shown in Table II below.

TABLE ll Grease Bomb Oxidation Test (ASTM D-942) Hours to 25 psiAntioxidant Conc., Wt.% Pressure Drop 6. Control grease 0 68 7. C -sec.alkyl MDA 0.04 58 8. C -scc. alkyl MDA-TAR 0.04 85 9. C -scc. alkyl MDA0.04 54 10. C -scc. alkyl MDA-TAR 0.04 101 EXAMPLE 3 This exampleillustrates the antioxidant activity of the alkylated methylenedianilinetar residues of this invention when they are used in light lubricatingoils and also shows their superiority over corresponding alkylatedmethylenedianiline. The tests were carried out according to Federal TestMethod Standard 7918 dianiline tar containing about 10 percent by weightof Method 5308.6 for the measurement of corrosiveness These results showthe superiority of an alkylated methylenedianiline tar of this inventionover an alkylated methylenedianiline in light oil. As can be seen inTable III, the alkylated methylenedianiline at 0.05 weight percent leveloffered practically no protection to the oil (compare changes in lOOF.viscosity and the development in acidity) whereas the alkylatedmethylenedianiline tar at the same concentration provided goodprotection. Use of higher concentration (0.5 weight percent) ofalkylated methylenedianiline tar offers excellent oxidation protectionto the turbine oil.

The foregoing detailed description has been given for clarity ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to exact details shown anddescribed for obvious modifications will occur to one skilled in theart.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. Compositions consisting essentially of alkylated aromatic polyamineshaving the formula 2. Compositions according to claim 1 wherein R is a2-alkyl radical having the formula wherein R is an alkyl group havingfrom one to about eight carbon atoms.

3. Compositions according to claim 2 wherein R is 4. Compositionsaccording to claim 1 wherein n is from about 0.85 to about 0.99.

5. A lubricant comprising a lubricant base and a stabilizing amount ofcompositions consisting essentially of alkylated aromatic polyamineshaving the formula

2. Compositions according to claim 1 wherein R is a 2-alkyl radicalhaving the formula -CH(CH3)-R'' wherein R'' is an alkyl group havingfrom one to about eight carbon atoms.
 3. Compositions according to claim2 wherein R is
 4. Compositions according to claim 1 wherein n is fromabout 0.85 to about 0.99.
 5. A lubricant comprising a lubricant base anda stabilizing amount of compositions consisting essentially of alkylatedaromatic polyamines having the formula